guest ::
| Home > Publications database > Entwicklung geträgerter Ba$_{0,5}$Sr$_{0,5}$Co$_{0,8}$Fe$_{0,2}$O$_{3-\delta}$ Sauerstoff-Permeationsmembranen |
| Home > Publications database > Entwicklung geträgerter Ba$_{0,5}$Sr$_{0,5}$Co$_{0,8}$Fe$_{0,2}$O$_{3-\delta}$ Sauerstoff-Permeationsmembranen |
| Dissertation / PhD Thesis/Book | PreJuSER-19317 |
2011
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
ISBN: 978-3-89336-752-8
Please use a persistent id in citations: http://hdl.handle.net/2128/4527
Abstract: Oxygen Transport Membranes (OTMs) are a promising way of obtaining high-purity oxygen. Compared to conventional methods, membranes require less energy than cryogenic air separation. OTMs consist of gastight, ceramic, mixed ionic-electronic conductors (MIEC) and allow oxygen transport via oxygen vacancies in the crystal lattice. Therefore, the theoretically achievable purity of these OTMs is 100%. The most promising class of materials are the perovskites, which has a high ionic and very high electronic conductivity. The perovskite with the highest oxygen permeability is the Ba$_{0,5}$Sr$_{0,5}$Co$_{0,8}$Fe$_{0,2}$O$_{3-\delta}$ (BSCF), which has also been used in this work. Further potential for improvement of the oxygen permeation can be provided by a thin, supported membrane,an optimization of the microstructure of the porous support as well as by the use of porous activation layers on top of the membrane. An aim of the first part of the work is the development of thin membranes on top of a porous support. For this purpose, supports of different porosity and pore size were prepared by tape casting using different pore formers. The thin membrane layers were manufactured by screen printing and tape casting. The preparation of screen-printed membrane layers as well as porous activation layers was carried out on pre-sintered supports respectively sintered membranes. Composite membranes (thin membrane layer and porous support) were prepared by sequential tape casting and subsequent co-firing. Regarding deflection and leakage, the tape cast and co-fired membranes achieved the best results. The influence of membrane microstructure on oxygen permeation has been studied on composite membranes with 26%, 34% and 41% support porosity and 20$\mu$m and 70$\mu$m membrane layer thickness. This increase of support porosity as well as the reduction of membrane thickness led to an increase in the oxygen permeation. The increase of the oxygen permeation by decreasing the membrane layer thickness is lower than the Wagner equation would have suggested and this issue will be discussed in this chapter. Ways of reducing the limiting factors are to be sought in the use of porous surface layers, tailoring the support microstructure and in the use of vacuum conditions instead of a sweep gas on the support side. Limiting factors for oxygen transport through the composite membrane were identified and separated by systematic choice of the boundary conditions during permeation measurements. Limiting factors are surface transport processes, concentration polarization in the porous support and the transport through the membrane. From the acquired data, a transport model has been developed to describe the oxygen transport through the composite membrane.
|
The record appears in these collections: |
PDF
Fulltext by OpenAccess repository